Examples of electronic components using a ceramic material include capacitors, inductors, piezoelectric elements, varistors, thermistors, and the like.
Among ceramic electronic components, multilayer ceramic capacitors (MLCC) may be used in various electronic devices, due to advantages thereof such as a compact size, high capacitance, ease of mounting, and the like.
For example, a multilayer ceramic capacitor may be used in a chip type condenser mounted on a printed circuit board of various types of electronic products such as imaging devices, liquid crystal displays (LCDs) or plasma display panels (PDPs), computers, personal digital assistants (PDAs), and mobile phones, serving to charge or discharge electricity therein or therefrom.
Such a multilayer ceramic capacitor may have a structure in which a plurality of dielectric layers and internal electrodes having different polarities are stacked alternatingly.
In this case, since the dielectric layers may have piezoelectric properties, when a direct current (DC) or alternating current (AC) voltage is applied to the multilayer ceramic capacitor, a piezoelectric phenomenon may be generated in the dielectric layers interposed between the internal electrodes, thereby causing periodic vibrations due to a volume of a capacitor body expanding and contracting according to a frequency of the voltage.
These vibrations may be transferred to a printed circuit board through external electrodes of the multilayer ceramic capacitor and a soldering material connecting the external electrodes to the printed circuit board. The entire printed circuit board may act as an acoustic reflective surface to generate a vibration sound, which the user experiences as noise. This vibrated sound may have a frequency corresponding to an audio frequency in a region of 20 to 20,000 Hz, which may cause listener discomfort and is referred to as acoustic noise.
Furthermore, in recent electronic devices, since attempts to reduce noise of equipment components have been ongoing, acoustic noise generated in multilayer ceramic capacitors as described above may become more noticeable.
When the operating environments of equipment are relatively silent, users may regard such acoustic noise as abnormal sound, and thus may mistakenly believe the noise of acoustic noises to signal the breakdown of equipment. In addition, in devices having voice circuits, acoustic noise may overlap with audio output, thereby leading to deterioration in the quality of the devices.